Hemodynamic neuroimaging methods (PET, fMRI) have poor temporal resolution. Blood flow changes too slowly (over several sec6nds) to track dynamic cognitive processes. This limitation is important in neuropsychological studies of aging. Even when measures of abstract cognition, memory, or flexibility show no effects of normal aging, the older person is consistently found to be slower than the young person. Furthermore, assessing the early mental decline of Alzheimer's Dementia would benefit from a neuroimaging technology to track the premature slowing of specific memory functions. We propose to develop an advanced dense sensor array electroencephalographic (EEG) system that is optimized for integration with whole-head magnetoencephalographic (MEG) systems. We introduce a 256-channel sensor net that achieves low magnetic noise with carbon-fiber electrodes and a physiological amplifier that is engineered for high scalp impedance sensors and low magnetic interference. Most importantly, we propose a fully electromagnetic signal analytic strategy, in which the differing advantages of electrical and magnetic fields are combined within a single turnkey software package. Although the proposed electromagnetic neuroimaging system would be sold initially to research laboratories, advances in understanding the changes in the time course of mental operations in the aged brain will have significant clinical applications. PROPOSED COMMERCIAL APPLICATIONS: By tracking neurophysiological slowing with rnillisecond precision, dense array MEG/EEG could optimize our understanding of neurological disorders of the aged, leading to accurate assessment of dementing illness when treatment is still useful.